Substituted heterocycle fused gamma-carbolines and their pharmaceutically acceptable salts are represented by the core structure shown in Formula 1J:

These compounds are disclosed in WO 2000/77010; WO 2000/77002; WO 2000/77001; U.S. Pat. Nos. 6,713,471; 6,552,017; 7,081,455; 6,548,493, 7,071,186; Reissue U.S. Pat. Nos. 39,680; 39,679; and U.S. Provisional Application No. 60/906,473, the contents of each of which are herein incorporated by reference in their entirety. These compounds have been found to be useful as 5-HT2 receptor agonists and antagonists used in treating disorders of the central nervous system including a disorder associated with 5HT2C or 5HT2A receptor modulation selected from obesity, anorexia, bulemia, depression, a anxiety, psychosis, schizophrenia, migraine, obsessive-compulsive disorder, sexual disorders, depression, schizophrenia, migraine, attention deficit disorder, attention deficit hyperactivity disorder, obsessive-compulsive disorder, sleep disorders, conditions associated with cephalic pain, social phobias, gastrointestinal disorders such as dysfunction of the gastrointestinal tract motility.
As a free base, substituted heterocycle fused gamma-carbolines exist in liquid form and are susceptible to N-oxidation and/or degradation. Such unstable characteristics could render these compounds undesirable as pharmaceutical products. The prior art discloses a large number of substituted heterocycle fused gamma-carboline derivatives in free base form as well as a large number of pharmaceutically acceptable salts, including hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric, nitric and the like; and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, sulfanilic, 2-acetoxybenzoic, fumaric, toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, isethionic, and the like. Of the large numbers of possible pharmaceutically acceptable salt compounds disclosed in the prior art, none were shown to have particular stability or desired properties. Because many pharmaceutical compounds can exist in different physical forms (e.g., liquid or solid in different crystalline, amorphous, polymorphous, hydrate or solvate forms) which can vary the stability, solubility, bioavailability or pharmacokinetics (absorption, distribution, metabolism, excretion or the like) and/or bioequivalency of a drug, it is of critical importance in pharmaceutical development to identify a pharmaceutical compound of optimal physical form (e.g., free base or salt in solid, liquid, crystalline, hydrate, solvate, amorphous or polymorphous forms).